Azobenzene as conformational switch in model peptides

The photoinduced isomerization of ozobenzene between the extended (trans) and compact (cis) conformations is reversibly triggered by light of two differing wavelengths. The resulting changes in molecular geometry have been extensively utilized to photoswitch transformations in chemical species reversibly for applications in optoelectronic devises as well as to photocontrol conformotional states in (bio)polymers. The high isomerization yield, remarkable photostability and ultrafast kinetics (few ps) of ozobenzene are well suited for the design of small, defined model systems that allow detailed folding studies to be carried out both experimentally and theoretically on the some molecules. In our andother laboratories such systems were recently obtained with cyclic peptides of defined conformational preferences as well as with a-helical and P-hairpin peptides. These should, by comparison of simulation and experiment, permit an assessment and improvement of the theoretical description on the one hand and a detailed interpretation of the ultrafast conformational dynamics on the other. The phototriggered changes in conformational states lead to concurrent changes in biophysical properties that can be exploited in the photocontrol of biochemical and biological events, as exemplarily discussed with redox-active cyclic biscysteinyl peptides and receptor ligands.